cross a bridge when you come to it

cross a ˌbridge when you ˈcome to it

,

cross your ˌbridges when you ˈcome to them

deal with a problem only when it happens and not worry about it before then: ‘What will you do if you can’t afford to run your car next year?’ ‘I’ll cross that bridge when I come to it.’
See also: bridge, come, cross